1. Field of the Invention
This invention relates to a developing apparatus used in an image forming apparatus using the electrophotographic method or the electrostatic recording method to develop an electrostatic image on an image bearing member.
2. Related Background Art
The following known method has heretofore been used as a method of applying a developer to a developing sleeve in the developing apparatus of an electrophotographic image forming apparatus.
That is, a magnet having strong and weak magnetic fields at the circumferential positions thereof is disposed in the central portion of a developing sleeve, and a developing blade formed of a magnetic material is disposed at a position corresponding to the peak of one of these magnetic fields, and this developing blade is fixed to a developing container so as to keep a minute gap of hundreds of xcexcm from the surface of the developing sleeve uniformly in the lengthwise direction thereof.
On the other hand, the developer in the developing container is always carried to the developing sleeve side by an agitating member in the developing container. Here, the developer comprises a magnetic material and is attracted to the surface of the developing sleeve by the magnet in the developing sleeve. The attracted developer is carried on the developing sleeve rotatively driven, and arrives at the minute gap between the developing sleeve and the developing blade, and uniformly coats the surface of the developing sleeve in this minute gap and also is frictionally charged by the frictional contact (slide) in the minute gap.
In the case of a so-called high-speed machine for achieving the higher speed of productivity, it is necessary to increase the linear speed (process speed) of an image bearing member for forming an image as a latent image and at the same time, it is also necessary to increase a speed for developing the latent image. Specifically, it is necessary to increase the linear speed of the developing sleeve. As a result, the amount of frictional contact of the developer increases in the minute gap between the developing sleeve and the developing blade, and this causes the heat generation (hereinafter referred to as the developing frictional contact heat) of the developer near the developing sleeve or on the surface of the developing sleeve.
Thus, when the high-speed electrophotographic image forming apparatus is continuously operated, the abnormal heat generation of the developer becomes more remarkable, and the deterioration of the developer progresses with endurance and this results in a reduction in developing density, and in the worst case, there arises the problem that the developer is fused onto the developing sleeve.
In order to solve the above-noted problem, there has been proposed a method of bringing a heat sink for radiation into contact with the developing blade, or forcibly cooling the developing blade by cooling means, but for example, it is not easy to uniformly cool the lengthwise direction of the heat sink for radiation by a cooling fan, and on the contrary, there is anticipated such a reverse effect of providing temperature unevenness.
It is an object of the present invention to provide a developing apparatus in which the temperature rise of a developing blade is restrained.
It is another object of the present invention to provide a developing apparatus in which the temperature unevenness of a developing blade is prevented.
It is still another object of the present invention to provide a developing apparatus comprising:
a developer carrying member for carrying a developer thereon;
a regulating member for regulating an amount of the developer on the developer carrying member; and
a heat pipe provided along a lengthwise direction of the regulating member.
Further objects of the present invention will become apparent from the following description.